1. Technical Field
The present invention relates to a heating cabin used to maintain processed good warm for a long time without causing change in quality thereof.
2. Prior Art
Ready-made food articles such as box lunches or side dishes are usually cooked in food processing workshops in a time frame from midnight to early morning and delivered to supermarkets, convenience stores, general groceries, various jobsites or the like.
Such food articles are served usually after going through the process of cooking, cooling, transport, refrigeration, and heating. Such a process not only increases various costs but also disperses moisture content as well as original flavor from the food articles.
It is also well known to maintain food articles warm utilizing a heater or the like with the intention of preserving these articles for a long time. However, flavor and quality of the food articles inevitably change as time elapses and consequently these food articles are disposed after a predetermined time has elapsed.
Particularly in the case of side dishes, it has conventionally been considered the best measure that these articles should be maintained at a temperature of 80.degree. C. or higher. However, such a measure has been found to be ineffective. The food articles maintained at this excessively high temperature lose freshness as well as flavor and correspondingly give offensive smell as the time elapses. As a result, these food articles have their commercial value significantly lowered.
Obviously, a so called heating chamber is necessary to perform such a measure of temporarily maintaining a box lunch or a ready-made side dish at a desired temperature. The conventional heating cabin typically employs glass wool as insulating material placed on respective side walls thereof. With this heating cabin of prior art, a temperature emitted from heat generator means must be as high as 135.degree. C. to meet the requirement that the food articles should be maintained at a relatively high temperature, i.e., a temperature of 80.degree. C. or higher as has previously been mentioned.
In the typical heating cabin of well known art, the heat generator means is mounted directly on the side walls and glass wool used as the insulating material is directly exposed to the above-mentioned excessively high temperature emitted from the heat generator means. The critical temperature glass wool can resist is on the order of 80.degree. C., so this insulating material is deteriorated early due to the unacceptably high temperature.
Considering such state of art, the inventor has made studies on various aspects of the previously described problem and obtained therefrom findings as follows: The optimum temperature at which the food articles should be maintained in the heating cabin is from 63.degree. C. to 68.degree. C. The food articles are deteriorated in the heating chamber as the temperature exceeds 70.degree. C. Specifically, moisture of each food article is evaporated first from the outer surface of each good article, which correspondingly loses its original humidity, leading to change in quality as well as loss of flavor. The thermal affection on the insulating material placed on the respective side walls of the cabin can be alleviated by properly selecting the placement of the heat generator means and by sufficiently increasing an amount of the insulating material.
It is unavoidable that more or less differential temperature appears in the vertical direction within the heating chamber. Sometimes an appropriate measure should be taken to compensate for this differential temperature, since a serious problem may result therefrom, depending on the type of food article to be handled.
Accordingly, it is a principal object of the invention to provide a heating chamber improved so that the temperature prevailing within the chamber can be maintained in the previously specified range, a secular change of the insulating material can be minimized and a useful life of the cabin can be prolonged as remarkably as possible.
It is another object of the invention to provide a heating cabin improved so that the differential temperature possibly appearing within the chamber can be minimized and thereby the temperature within the chamber can be maintained uniform.